dt-bindings: Document img,boston-clock binding

Add device tree binding documentation for the clocks provided by the
MIPS Boston development board from Imagination Technologies, and a
header file describing the available clocks for use by device trees &
driver.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Cc: linux-clk@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16482/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Documentation/devicetree/bindings/clock/img,boston-clock.txt

@@ -0,0 +1,31 @@
+Binding for Imagination Technologies MIPS Boston clock sources.
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+The device node must be a child node of the syscon node corresponding to the
+Boston system's platform registers.
+
+Required properties:
+- compatible : Should be "img,boston-clock".
+- #clock-cells : Should be set to 1.
+  Values available for clock consumers can be found in the header file:
+    <dt-bindings/clock/boston-clock.h>
+
+Example:
+
+	system-controller@17ffd000 {
+		compatible = "img,boston-platform-regs", "syscon";
+		reg = <0x17ffd000 0x1000>;
+
+		clk_boston: clock {
+			compatible = "img,boston-clock";
+			#clock-cells = <1>;
+		};
+	};
+
+	uart0: uart@17ffe000 {
+		/* ... */
+		clocks = <&clk_boston BOSTON_CLK_SYS>;
+	};